.indexWeb{
    background: url(../img/bg-img.png)no-repeat;
    background-size: cover;
    .cloud{
        position: relative;
        top: 50%;
        right: -40%;
        animation-name: yundong;
        animation-duration: 10s;
        animation-iteration-count: infinite;
    }
    @keyframes yundong{
        0%{
            right: -40%;
             opacity: 1;
        }
        90%{
            right: 100%;
            opacity: 0;
        }
        100%{
            right: -40%;
            opacity: 0;
        }
    }
}
